You are making a good choice on ammo.
As has already been mentioned, it takes crushed bone or preferably a centeral nervous system hit to stop a big bear. The 44 mag can do it but needs a bullet that will penetrate (non expanding). The heavy for caliber (over 300gr for the 44 mag) hardcast bullet with a wide meplat is the tool for the job.
The question as others have already said is can the shooter do it. Truth is most guys aren't up to the task. It's not a mach thing, they simply don't shoot enough with full power ammo. It's expensive & time consuming. Since the average guy can't shoot a heavy loaded 44 mag well, going up the the 454 which is much meaner to the shooter only makes it worse.
Because of that the shotgun with hard (not deer) slugs is often the better choice, but will it be easy to lay hands on in a second or two if needed or laying against a tree, tied to the pack, left in the truck, etc.? I have a Marlin Guide Gun like Mojo mentioned & love it, but with a loaded magazine it ways around 8# & even as short as it is it's a little cumbersome (I still like it batter than a shotgun).
All that adds up to pepper spray probably being more efficient for the average guy.